1. Field of the Invention
The present invention relates to an electronic circuit provided with a plurality of circuit elements performing a specified basic function and its adjusting method, including an analog filter circuit and its adjusting method, a high-frequency circuit and its adjusting method, and an integrated circuit and its adjusting method. The present invention can be effectively applied to an electronic circuit in which analog values such as the amplitude, phase, frequency of a signal are important.
2. Related Art
Previously, (1) effort in a circuit design, (2) adjustment of adjusting points provided on an electronic circuit, (3) effort to reduce errors in production of a semiconductor integrated circuit and (4) selection of manufactured electronic circuits have been used as methods for improving the accuracy attained by an electronic circuit in producing a target value.
However, method (1), making an effort in a circuit design, needs to be repeated until a good result can be obtained. The design process is repeated until variation in the function of an electronic circuit caused by variation in characteristics of elements forming the electronic circuit becomes as insensitive as possible. In the case that a target function has a high energy content, it is necessary to exactly grasp such parameters as transfer characteristics of the circuit elements and when it is difficult to do so, it is technically difficult to design such a circuit.
Moreover, since there is also the method of item (2), adjusting points are provided on an electronic circuit. Usually, the number of adjusting points is made as small as possible during of design. In case the number of adjusting points becomes large, an effort in a circuit design is made so that adjustment results are independent of one another, as shown in FIG. 2(a). But when performing such a circuit design that makes it possible to obtain adjustment results independent of one another this method has an advantage of making adjustment easy. But, on the other hand, it requires a special circuit design to obtain its adjustment results. Additionally, the circuit design becomes complicated and needs to adopt a number of high-accuracy elements. For example, adding a trimmer capacitor TC at a point of a signal source impedance Z where a signal s appears, it is possible to adjust the phase delay quantity of the signal s but at the same time as this adjustment occurs, the amplitude of this signal is also changing. In order to change only the phase and not to change the amplitude, it is necessary to add a circuit for compensating for the amplitude change or to use a separate complicated phase delay adjustment circuit.
A circuit to make only a single parameter variable as described above, or a circuit to perform compensation so as to make only a single parameter variable is here referred to as an xe2x80x9cequalizing circuitxe2x80x9d. An equalizing circuit needs a greater number of circuit elements in comparison with a simple circuit and often needs more accurate elements.
Therefore, the prior method is expensive in design cost and long in design time. And it is sometimes necessary to adopt expensive elements that are highly redefined in an electronic circuit when designing the circuit.
Further, when adjusting the adjusting points of item (2), the effects which adjustment points have on circuit characteristics are not independent of one another as shown in FIG. 2(b). When the design is simple, a small number of elements can do and high-accuracy elements are not necessary. However, it is still necessary to divide an electronic circuit into very small parts and adjust operation of the electronic circuit individually. With these small parts, the adjustment is very complicated and when individual measurements cannot be performed, the adjustment is very difficult.
Sometimes, when a plurality of adjusting points, as described above, cannot be adjusted independently of one another, the size of an adjustment range has the same number of dimensions as the number of adjusting points linked with one another, the adjusting and search space expands in proportion to the number of adjusting points at an exponential rate. The adjustment then requires an impractical time or becomes impossible. Considering as an example, a case in which there are ten adjusting points to be adjusted by a setting signal of 8 bits and all of them are linked to one another. The search space for adjustment has an enormous number of combinations of xe2x80x9c2{circumflex over ( )}80≈10{circumflex over ( )}24xe2x80x9d, and it has been impossible using the prior methods to perform adjustment in a practical time.
Additionally, a pre-set resistor or trimmer capacitor used at an adjusting point can be made large in size so that it can be operated by an adjusting bar or the like in order to adjust a parameter by a mechanical means. Such a method has a disadvantage that it is expensive to adjust. Furthermore, an alternate adjustment method using a laser trimming operation gives a physically unrestorable change to the adjusting point. Thereafter, once the circuit fails in adjustment the electronic circuit cannot adjusted.
Last, the method of making errors in production small in item (3) is problematic in that there is limitation in processing accuracy of a semiconductor material. A high-accuracy process is expensive.
And the method of selecting electronic circuits in item (3) has a problem, since an electronic circuit whose function does not meet the specified target value is treated as a defective product and is generally discarded, the electronic circuit manufacturing process can be very low in its yield rate and becomes remarkably uneconomical.
Furthermore, considering individual circuits, an analog filter circuit (filter circuit) performs a process of removing a specific frequency-band signal component of an input signal or a process of taking out only a specific frequency-band signal component (filtering process). In the case of mass production it sometimes occurs that individual filter circuits vary greatly in filter characteristics due to irregularities in material and manufacturing errors. Then a desired signal component and an unnecessary signal component (a frequency component out of the passing band of a filter circuit) are sometimes not completely separated. Filter circuits have been made into an LSI (large scale integrated circuit) in recent years. Since such an LSI filter circuit cannot replace individual components, an LSI filter circuit whose filter characteristics are not within an acceptable range is treated as a defective product and discarded.
A mixer circuit sometimes outputs unnecessary signal components (image frequency components, local oscillation frequency components, harmonic components of a total frequency or a differential frequency of the mixer circuit) due to variation in characteristics of circuit elements.
Since a high-frequency circuit handles a signal having high-frequency components (radio frequency components of 100 kHz or higher in general), it has a problem of parasitic inductance and parasitic capacitance. Furthermore, it often needs to consider frequency dependence in transfer characteristics of a circuit elements, and scattering and reflection of a signal at a characteristic impedance discontinuity point. Therefore, it has typically required a long time for design and manufacture, and has been high in development cost and manufacturing cost.
A high-frequency integrated circuit is a circuit obtained by integrating a high-frequency circuit conventionally composed of discrete components into an LSI by means of a semiconductor integrated circuit technology. In order to attain a specified performance in this integrated circuit, it is necessary to perform impedance matching and accurately set the parameters of individual electronic circuits contained in the integrated circuit to specific values. In order to do so, it is necessary to know accurate parameter values of circuit elements and exactly manage its manufacturing process, and therefore a high-frequency integrated circuit has needed a longer time for design and manufacture, and a higher development cost and higher manufacturing cost in comparison with a low-frequency integrated circuit.
In conventional integrated circuit design, a designed circuit has been verified by performing simulations of circuit operations by means of a computer. However, it is impossible to exactly simulate nonlinearly of element parameters, interference among signals in a substrate and additionally delay caused by parasitic capacitance or parasitic inductance in the case of handling a high frequency. Practically it has been necessary to evaluate characteristics of an integrated circuit manufactured on an experimental basis and redesign it. Therefore, conventional methods require a long time for design and manufacture, and have a high development and manufacturing cost.
Attempts to apply a genetic algorithm to optimization of an electronic circuit have been performed. Those conventional attempts have been performed to determine the layout of an electronic circuit by means of a genetic algorithm at the time of a circuit design. However, the former method has been applicable only when simulations of a circuit operation can be performed completely without error on a computer. When analog values of signals are important, therefore, the above-mentioned technique has been unsuccessful.
In consideration of the above-mentioned points, therefore, an object of the present invention is to provide an electronic circuit and its adjusting method capable of obtaining a higher function and higher performance than the prior art with less design labor than the prior art even when parameters of circuit elements cannot be exactly grasped or when errors occur in parameters of circuit elements in a manufacturing process, and furthermore to provide a method for preventing deterioration in function and performance of an electronic circuit caused by variation of circuit elements.
In order to attain the above-mentioned goals, an electronic circuit, like its concept shown in FIG. 1, is characterized by an electronic circuit, being provided with a plurality of circuit elements and performing a specified basic function, wherein a plurality of specific circuit elements 2 related to a basic circuit 3 performing said specified basic function out of said plurality of circuit elements are composed of circuit elements changing their element parameters according to values indicated by control signals and said electronic circuit 1 is provided with a plurality of holding circuits 5 for holding a plurality of control signals to be given, for example, through digital/analog (D/A) converter circuits 4 to said plurality of specific circuit elements 2, and the values of said plurality of control signals which said plurality of holding circuits 5 hold are changed by external apparatuses 8 and 9 according to a probabilistic searching technique so that said basic function of said electronic circuit 1 satisfies designated specifications. In FIG. 1, symbol 6 is an input terminal of the basic circuit 3 and symbol 7 is an output terminal of the basic circuit 3.
A method for adjusting an electronic circuit of the present invention, its concept shown in FIG. 1, is characterized by a method for adjusting an electronic circuit 1 being provided with a plurality of circuit elements and performing a specified basic function, wherein a plurality of specific circuit elements 2 related to a basic circuit 3 performing said specified basic function out of said plurality of circuit elements are composed of circuit elements changing their element parameters according to values indicated by control signals, and a plurality of holding circuits 5 provided in said electronic circuit 1 hold a plurality of control signals to be given, for example, through digital/analog (D/A) converter circuits 4 to said plurality of specific circuit elements 2, and the values of said plurality of control signals which said plurality of holding circuits 5 hold are changed by external apparatuses 8 and 9 according to a probabilistic searching technique so that said basic function of said electronic circuit 1 satisfies designated specifications.
According to such an electronic circuit and its adjusting method, a plurality of specific circuit elements 2 related to a basic circuit 3 performing said specified basic function out of said plurality of circuit elements of an electronic circuit 1 performing said specified basic function are composed of circuit elements changing their element parameters according to values indicated by control signals, and a plurality of holding circuits 5 provided in said electronic circuit 1 hold a plurality of control signals to be given, for example, through digital/analog (D/A) converter circuits 4 to said plurality of specific circuit elements 2, and the values of said plurality of control signals which said plurality of holding circuits 5 hold are changed by external apparatuses 8 and 9 according to a probabilistic searching technique so that said basic function of said electronic circuit 1 satisfies the designated specifications, and therefore even in case that circuit element parameters related to said basic circuit 3 performing said specified basic function cannot be exactly grasped or in case that errors occur in circuit element parameters in a manufacturing process, it is possible to obtain a higher function and higher performance with respect to its basic function than the prior art with less design labor than the prior art and furthermore it is possible also to prevent deterioration in function and performance of an electronic circuit caused by variation of circuit elements.
The performance of an electronic circuit can be represented by a function F having as a parameter the transfer characteristic of each of a plurality of adjustable circuit elements which the electronic circuit is provided with. Making the function of an electronic circuit satisfy the designated specifications is equivalent to finding a solution for the function F. The present inventors pay attention to this point and have found that a genetic algorithm can be applied to adjustment of an electronic circuit.
A genetic algorithm is an algorithm which uses probabilistic searching techniques and (1) effectively works on a wide area search, (2) does not need such derivative information as differential values other than an evaluation function F, and (3) is easy to install. Therefore, the present invention may use a genetic algorithm in changing values of a plurality of control signals by said external apparatuses 8 and 9.
In the case that evaluation function F satisfies a specific condition, it is possible to improve a searching efficiency by using a simulated annealing method (one of the probabilistic searching techniques used in place of a genetic algorithm). Therefore, the present invention may use a simulated annealing method in changing values of a plurality of control signals by said external apparatuses 8 and 9.
And the present invention may use an evaluation function for weighting and integrating a plurality of evaluation results of said electronic circuit 1 when external apparatuses search the optimum values.
An electronic circuit of the present invention is characterized that in the electronic circuit 1, the electronic circuit itself is provided with a setting means instead of using external apparatuses 8 and 9, and a method for adjusting an electronic circuit of the present invention is characterized in that the values of a plurality of control signals are changed by said setting means provided in said electronic circuit instead of using external apparatuses 8 and 9 in a method for adjusting an electronic circuit. According to an electronic circuit of the present invention and a method for adjusting an electronic circuit of the present invention, the same action and effect as said electronic circuit and its adjusting method can be obtained. Moreover, since a setting means provided in the electronic circuit itself is used in place of external apparatuses, it is possible to further make it possible to perform adjustment by using only the electronic circuit at any time and place.
These electronic circuits and their adjusting methods of the present invention may use a genetic algorithm in changing the values of a plurality of control signals by said setting means.
And these electronic circuits and their adjusting methods of the present invention may use a simulated annealing method in changing the values of a plurality of control signals by said setting means.
Moreover, these inventions may use an evaluation function for weighting and integrating a plurality of evaluation results of said electronic circuit when a setting means searches the optimal values.
And an electronic circuit of the present invention as described above and a basic circuit 3 in a method for adjusting an electronic circuit of the present invention may be an analog filter circuit, and particularly may be a Gm-C filter circuit.
Furthermore, an electronic circuit of the present invention and a basic circuit 3 in a method for adjusting an electronic circuit of the present invention may be a high-frequency circuit, and may be an integrated circuit, and an integrated circuit in this case may be a high-frequency integrated circuit in particular.